This image shows spectral information collected from the Earth's moon.
Click on image for full size NASA

Spectra

Minerals of a planet's surface, and molecules of an atmosphere emit light of various wavelengths. The wavelengths of light which minerals or molecules emit is characteristic of each individual mineral or molecule, and is called that mineral or molecule's spectra. Thus the spectra of a mineral or molecule is like a human fingerprint, and can be used to identify it.

When studying the planets, scientists have designed instruments which can collect separate wavelengths of light. The light received from a planet is separated by means of a mirror or several mirrors, into separate wavelengths. Instruments such as these help scientists determine what a planet is made out of. Such an instrument is called a spectrometer.

The image to the left of the Earth's moon was made by examining the moon through different wavelengths of light, then recombining them into one picture. Some minerals emit more light in the blue than the red, and so on. These minerals stand out in the picture. The colors of the picture are enhanced to better show the contrast. Pink is very old, pulverized terrain, oranges and blues are lunar lava flows composed of granite-like rock, light blue are mineral-rich deposits associated with meteorite impacts.

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